F113 ... F115                
    F260 ... F265                
    F247 ... F248                
    GIS PCB BITS              
    GIS CMT-BITS             
    OTHER TYPES            
 Router bits? Some hints on selection

Premium bits by GIS  

Why it is fine if your router bit has many cutting edges ...
1. The cutting edge is the wear part of your bit. The more cutting edges ou have, the more share the wear, the longer normally your bit lasts (="tool lifetime").

2. A cutting tool with several cutting edges is better balanced as a bit with only one edge.

The bigger cross section area covered by carbide (instead of "air") allows an easier transportation of the heat caused by the cutting process towards the chuck and the spindle. This is especially valuable if there is no further possibility to cool the tool.

The more cutting edges your cutter has, the smaller the chips, the smoother normally the surface of your workpiece will be.

Why it is fine if your router bit has just one cutting edge ...
1. The main problem within the process of milling a slot is adhesion of chips within the chipflute of the tool and obstruction of the tool caused by this. Once obstructed the bit will no longer transport the chips towards the surface of the material and the feed force of the machine brakes it. That may happen - depending on the material - long before the cutting edge is dull. So the most important question is: "Which way the chips shall go?". Common answer: "Upwards or th the back of the cutter into the slot" (exempt: downcut bit). For this reason you need space (=chipflute), to carry the chips away. The comparison of the cross-section of various types shows that a single tooth cutter provides the largest open area (= biggest cipflute) and that the open area descends with the increase of the number of cutting edges.

2. When milling aluminium or plastics the application of single flute cutters with polished cutting edges and chipflutes has proven to be the best choice, normally. The polished surface of the chipflute makes it almost impossible for the chips to aggregate to the surface of the cutter or to create a built-up edge (aluminium).

3. The less cutting edges a router bit has the easier the plunge operation into the material will be.

What is more important?
The question what will be the most suitable cutter for a certain application can only be answered by examining the whole process including the routing system, its spindle, cooling, clamping, chip removal, etc. So this can only be a rough rule of thumb: For cutting plastics (PVC, acrylic, cellular foam plastic), wood and wooden composits (chipboard), non-ferrous metals (soft aluminum, aluminium composits, copper, brass, ...) normally a one flute cutter will be the best choice because the problem of cutting edge erosion remains far behind the problem of obstruction.

Foy very hard plastics or aluminium alloys (short chipping) a two fluted bit may be the better choice, but always take care for excellent smooth and sharp cutting edges and large chipflutes.

For steel normally you will use a bit with 4 or more cutting edges, the number depends a little on the diameter of your cutter. In our opinion the application of a tool with more than 2 cutting edges will be of advantage only if the cutting diameter is equals or larger than Ø 6 mm

Router bits: Single Flute router in cross-section
One flute cutter in cross-section:
The cutter shows a large open area.


Router bits: Three flute router in cross-section
Three flute cutter in cross-section:
The 3 cutting edges cover a lot more of the space.


GIS Gienger Industrie-Service • Segantinistr. 5 • CH - 8049 Zürich • Tel. / Fax +41-(0)44-341 5028 • mail:
Auslieferungslager EU • Weimarstr. 15 • D - 78532 Tuttlingen • Tel. +49-(0)7461-162020 • Fax 162021